The present invention relates to a method for producing 3,5-dimethyldodecanoic acid which is a sex pheromone of California prionus (Prionus californicus).
Sex pheromones of insects are usually bioactive substances released by individual females and having a function of attracting individual males. They show high attracting activity even in small amounts. Sex pheromones are widely used as a means for predicting the outbreak of insects or finding geological diffusion thereof (emergence into specific areas) or as a means for pest control. As a means for pest control, control methods called “mass trapping”, “lure & kill or attract & kill”, “lure & infect or attract & infect”, or “mating disruption” have been widely carried out in practice. To utilize a sex pheromone, economical production of a required amount of an active ingredient of the pheromone is necessary for basic research and further for a practical application.
California prionus (Prionus californicus), one of long horn beetles, has a wide distribution in Northwestern America. It is an insect pest to various kinds of perennial plants. Among them, damage by this insect pest to hops has been a serious problem. This insect pest has a life cycle as long as 3 to 5 years but it spends most of its life as a larva in soil, more specifically, in the roots or trunks of plants such as hop to be damaged by the insect pest so that it cannot be controlled easily by agrichemicals.
Millar et al. have revealed that as a result of syntheses of candidate compounds presumed from the mass spectra of an extract from this insect pest, the sex pheromone of the insect pest is 3,5-dimethyldodecanoic acid (J. Chem. Ecol., 2009, 35, 590-600). Also in this journal article, Millar et al. synthesize this product by bromination of 2-methyl-1-nonanol, subsequent conversion into a corresponding Grignard reagent, and then reaction with β-butyrolactone.
Further, Petrov et al. synthesize 3,5-dimethyldodecanoic acid by coupling between heptyl magnesium bromide and 2-chloro-3-pentene, addition of hydrogen bromide, alkylation of ethyl malonate, hydrolysis of the resulting ester, and decarboxylation (Fette, Seifen, Anstrichmittel, 1959, 61, 940-946).
Still further, Millar et al. stereoselectively synthesize a (3R,5S)-form and a (3S,5R)-form of 3,5-dimethyldodecanoic acid by asymmetric 1,4-addition of methyl magnesium bromide to 2-decenoate ester, reduction of the ester, a Wittig reaction, asymmetric 1,4-addition again of methyl magnesium bromide to the unsaturated ester thus obtained, and finally hydrolysis of the ester (J. Chem. Ecol., 2011, 37, 114-124).